Apparatus for an optimized plasma chamber top piece

ABSTRACT

A plasma processing system for processing a substrate is described. The plasma processing system includes a bottom piece including a chuck configured for holding the substrate. The plasma processing system also includes an induction coil configured to generate an electromagnetic field in order to create a plasma for processing the substrate; and an optimized top piece coupled to the bottom piece, the top piece further configured for a heating and cooling system. Wherein, the heating and cooling system is substantially shielded from the electromagnetic field by the optimized top piece, and the optimized top piece can substantially be handled by a single person.

REFERENCE TO RELATED APPLICATIONS

This application incorporates by reference U.S. Ser. No. 10/232,564(LAM2P364/P0990) filed on Aug. 30, 2002.

BACKGROUND OF THE INVENTION

The present invention relates in general to substrate manufacturingtechnologies and in particular to an apparatus for an optimized plasmachamber top piece.

In the processing of a substrate, e.g., a semiconductor substrate or aglass panel such as one used in flat panel display manufacturing, plasmais often employed. As part of the processing of a substrate for example,the substrate is divided into a plurality of dies, or rectangular areas,each of which will become an integrated circuit. The substrate is thenprocessed in a series of steps in which materials are selectivelyremoved (etching) and deposited (deposition) in order to form electricalcomponents thereon.

In an exemplary plasma process, a substrate is coated with a thin filmof hardened emulsion (i.e., such as a photoresist mask) prior toetching. Areas of the hardened emulsion are then selectively removed,causing components of the underlying layer to become exposed. Thesubstrate is then placed in a plasma processing chamber on a substratesupport structure comprising a mono-polar or bi-polar electrode, calleda chuck or pedestal. Appropriate etchant source are then flowed into thechamber and struck to form a plasma to etch exposed areas of thesubstrate.

Referring now to FIG. 1, a simplified diagram of inductively coupledplasma processing system components is shown. Generally, the plasmachamber (chamber) 102 is comprised of a bottom piece 150, a top piece144, and a top piece cover 152. An appropriate set of gases is flowedinto chamber 102 from gas distribution system 122. These plasmaprocessing gases may be subsequently ionized to form a plasma 110, inorder to process (e.g., etch or deposition) exposed areas of substrate114, such as a semiconductor substrate or a glass pane, positioned withedge ring 115 on an electrostatic chuck (chuck) 116. Gas distributionsystem 122 is commonly comprised of compressed gas cylinders 124 a-fcontaining plasma processing gases (e.g., C₄F₈, C₄F₆, CHF₃, CH₂F₃, CF₄,HBr, CH₃F, C₂F₄, N₂, O₂, Ar, Xe, He, H₂, NH₃, SF₆, BCl₃, Cl₂, WF₆,etc.).

Induction coil 131 is separated from the plasma by a dielectric window104, and generally induces a time-varying electric current in the plasmaprocessing gases to create plasma 110. The window both protectsinduction coil from plasma 110, and allows the generated RF field 142 togenerate an inductive current 111 within the plasma processing chamber.Further coupled to induction coil 131 is matching network 132 that maybe further coupled to RF generator 134. Matching network 132 attempts tomatch the impedance of RF generator 134, which typically operates atabout 13.56 MHz and about 50 ohms, to that of the plasma 110.Additionally, a second RF energy source 138 may also be coupled throughmatching network 136 to the substrate 114 in order to create a bias withthe plasma, and direct the plasma away from structures within the plasmaprocessing system and toward the substrate.

Generally, some type of cooling system 140 is coupled to chuck 116 inorder to achieve thermal equilibrium once the plasma is ignited. Thecooling system itself is usually comprised of a chiller that pumps acoolant through cavities in within the chuck, and helium gas pumpedbetween the chuck and the substrate. In addition to removing thegenerated heat, the helium gas also allows the cooling system to rapidlycontrol heat dissipation. That is, increasing helium pressuresubsequently also increases the heat transfer rate. Most plasmaprocessing systems are also controlled by sophisticated computerscomprising operating software programs. In a typical operatingenvironment, manufacturing process parameters (e.g., voltage, gas flowmix, gas flow rate, pressure, etc.) are generally configured for aparticular plasma processing system and a specific recipe.

In addition, a heating and cooling plate 146 may operate to control thetemperature of the top piece 144 of the plasma processing apparatus 102such that the inner surface of the top piece 144, which is exposed tothe plasma during operation, is maintained at a controlled temperature.The heating and cooling plate 146 is formed by several different layersof material to provide both heating and cooling operations.

The top piece itself is commonly constructed from plasma resistantmaterials that either will ground or are transparent to the generated RFfield within the plasma processing system (e.g., aluminum, ceramic,etc.). Most top piece designs, however, are optimized for operationalperformance within the chamber itself, and not for other considerationssuch as ergonomic safety or general thermal performance.

For example, the existing upper portion of the 2300 plasma etch chamberis a monolithic piece of aluminum weighing about 75 lbs, making itsubstantially difficult to handle during removal, installation, andcleaning. It generally requires at least two workers using some type oflifting apparatus (i.e., winch, etc.) to safely remove the top piecefrom the plasma processing system.

Historically, since the relative manufacturing cost of the top piece wasjust a relatively small portion of the overall system cost, there hasbeen no incentive to re-design with smaller amount of material, hencelighter. However, there is growing concern over worker safety, as wellas the reduction of worker injuries and subsequently of workercompensation claims. That is, as plasma processing systems have becomemore sophisticated, many substrate manufactures are able to use fewerless skilled workers in order to save costs, increasing the likelihoodof accidental injury.

For example, the Safety Guidelines For Ergonomics Engineering OfSemiconductor Manufacturing Equipment (SEMI S8-0701), and theEnvironmental, Health, And Safety Guideline For SemiconductorManufacturing Equipment (SEMI S2-0302), which are both incorporated byreference, discuss design principles for the elimination or mitigationof ergonomic hazards in plasma processing systems.

In particular, ergonomic hazards should be designed out or otherwisereduced to the maximum extent practicable. Ergonomic hazards existwhenever the system design or installation results in task demands(e.g., manipulation of the top piece) that exceed the informationprocessing and/or physical capabilities of trained personnel. Inparticular, equipment should be designed to fit the physicalcharacteristics of 90% of the user population (e.g. from 5th percentilefemale through 95th percentile male in the country or region of use.)

Preventive maintenance is also an issue, since the relative heavy weightof the top piece makes the top piece difficult to manipulate, and henceproblematic to effectively clean during scheduled maintenance. Cleaningis further aggravated by the presence of plastic and stainless materialson the top piece that limit the types of available cleaning techniques.That is, although a particular cleaning chemical may effectively cleanthe residue from the top piece, the same chemical may also substantiallydamage the plastic materials or stainless steel.

In addition, correctly reseating the top piece after maintenance isoften difficult, since it must properly be aligned with the bottom piecesuch that a set of gaskets properly seal around the top piece. A slightmisalignment will preclude a proper mating, requiring the workers to tryto nudge the heavy top piece into place.

The volume of material in the top piece also tends to add a substantialthermal mass to the plasma processing system. Thermal mass refers tomaterials have the capacity to store thermal energy for extendedperiods. In general, plasma processes tend to very sensitive totemperature variation. For example, a temperature variation outside theestablished process window can directly affect the etch rate or thedeposition rate of polymeric films, such as poly-floro-carbon, on thesubstrate surface. Temperature repeatability between substrates is oftenimportant, since many plasma processing recipes may also requiretemperature variation to be on the order of a few tenths of degree C.Because of this, the top piece is often heated or cooled in order tosubstantially maintain the plasma process within established parameters.

As the plasma is ignited, the substrate absorbs thermal energy, which issubsequently measured and then removed through the cooling system.However, since the top piece has a relatively large thermal mass,temperature corrections by the cooling system may not be synchronizedwith temperature variations in the top piece. Subsequently, heat flowvariations may cause the substrate temperature to vary outside narrowrecipe parameters.

In addition, the location of the heating and cooling plate 146, as shownin FIG. 1, may interfere with electromagnetic field 142. As a highfrequency power is applied from the RF power generator 134 to the coil131, an electromagnetic field is generated, which subsequently generatesan inductive current 111 that creates and maintains the plasma. Althoughnot necessarily uniform, the heating and cooling plate 146 may interferewith the electromagnetic field and subsequently affect the uniformity ofplasma 110. That is, the resulting electric field may become radialdistorted which may result in a substantially non-uniform plasma densityacross the substrate, potentially affecting yield.

This condition becomes even more problematic as requirements for highcircuit density on substrates continue to escalate. For example, in aplasma etch process, if the plasma is not properly optimized, facetingmay occur. A facet is a non-linear profile of a feature on thesubstrate, such as with a trench sidewall. A region of low plasmadensity may not remove a sufficient amount of material from thesubstrate, subsequently reducing the size of a trench or via. Likewise,a region of high plasma density may remove an excess amount of materialfrom the substrate subsequently creating a cavernous undercut.

In view of the foregoing, there are desired methods and apparatus foroptimizing a process model in a plasma processing system.

SUMMARY OF THE INVENTION

The invention relates, in one embodiment, in a plasma processing system,to an apparatus for processing a substrate. The plasma processing systemincludes a bottom piece including a chuck configured for holding thesubstrate. The plasma processing system also includes an induction coilconfigured to generate an electromagnetic field in order to create aplasma for processing the substrate; and an optimized top piece coupledto the bottom piece, the top piece further configured for a heating andcooling system. Wherein, the heating and cooling system is substantiallyshielded from the electromagnetic field by the optimized top piece, andthe optimized top piece can substantially be handled by a single person.

These and other features of the present invention will be described inmore detail below in the detailed description of the invention and inconjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 shows a simplified diagram of a plasma processing system;

FIG. 2 shows a simplified diagram of a plasma processing system with aoptimized top piece, according to one embodiment of the invention; and

FIGS. 3A-3B show a simplified diagram of a optimized top piece,according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference toa few preferred embodiments thereof as illustrated in the accompanyingdrawings. In the following description, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one skilled in the art, thatthe present invention may be practiced without some or all of thesespecific details. In other instances, well known process steps and/orstructures have not been described in detail in order to notunnecessarily obscure the present invention.

While not wishing to be bound by theory, it is believed by the inventorherein that an optimized top piece can be configured to substantiallyoptimize worker ergonomic safety as well as plasma process operationalcharacteristics.

In one embodiment, the optimized top piece comprises a weight that isapproximately 80% less than the existing non-optimized top pieces.

In another embodiment, the optimized top piece comprises a heat capacitythat is approximately 80% less than the existing non-optimized toppieces.

In another embodiment, the optimized top piece shields the RF field froma heating and cooling plate.

In another embodiment, the optimized top piece consists of a lightweight, hard anodized, aluminum cylinder that has features for mountingprocess support hardware (RF input coil, alignment features, temperaturecontrol hardware, etc.), sealing vacuum and conducting electricalcurrent out of the optimized top piece.

In another embodiment, the optimized top piece comprises a set of topand bottom vacuum seals that include o-rings.

In another embodiment, the optimized top piece comprises a metallicspring gasket that substantially fits into a groove and contacts a baremetal strip on the bottom piece in order to establish electricalconduction.

In another embodiment, the internal shape of the optimized top piecesubstantially matches the internal shape of a non-optimized top piece,such that electrical, gas flow, and plasma containment characteristicsare substantially the same.

In another embodiment, the top piece does not substantially containplastic or stainless steel.

In another embodiment, the top piece complies with the SEMI ergonomicsafety standards for a part handled by a person.

Referring now to FIG. 2, a simplified diagram of inductively coupledplasma processing system components with an optimized top piece isshown, according to one embodiment of the present invention. Generally,the plasma chamber (chamber) 202 is comprised of a bottom piece 250 anda top piece cover 252. However, in a non-obvious fashion, top piece 144,as shown in FIG. 1, as been replaced with an optimized top piece 244, inorder to optimize worker ergonomic safety as well as plasma processoperational characteristics.

The top piece itself is commonly constructed from plasma resistantmaterials that either will ground or are transparent to the generated RFfield within the plasma processing system (e.g., aluminum, ceramic,etc.). Most top piece designs, however, are not optimized for ergonomicsafety or general thermal performance.

Historically, there has generally been no motivation to optimize toppiece weight, since the manufacturing cost of the top piece is generallya relatively small portion of the overall system cost. However, concernover worker safety has grown as industry is attempts to reduce workerinjuries and injury-related costs. In particular, as plasma processingsystems have become more sophisticated, many substrate manufactures areable to use fewer less skilled workers in order to save costs,increasing the likelihood of accidental injury. As previously explained,ergonomic hazards exist whenever the system design or installationresults in task demands (e.g., manipulation of the top piece) thatexceed the information processing and/or physical capabilities oftrained personnel.

However, in the current invention, an optimized top piece may beapproximately 80% lighter than an existing non-optimized top piece,substantially complying with SEMI ergonomic safety standards for a parthandled by one person (e.g., removing, lifting, cleaning, etc.). Inaddition, preventive maintenance is also substantially simplified, sincea single worker can easily manipulate the optimized top piece withoutthe use of a lifting apparatus (i.e., winch, etc.), facilitating propercleaning. In addition, correctly reseating the top piece aftermaintenance is also substantially simplified, since it may be easilyaligned with the bottom piece such that a set of gaskets properly sealaround the top piece.

The current invention also may have a thermal mass that is approximately80% less than the existing non-optimized top pieces. As previouslydescribed, the volume of material in the top piece also tends to add asubstantial thermal mass to the plasma processing system. Temperaturerepeatability between substrates is often important, since many plasmaprocessing recipes may also require temperature variation to be on theorder of a few tenths of degree C. Because of this, the top piece isoften heated or cooled in order to substantially maintain the plasmaprocess within established parameters. Unlike a non-optimized top piece,an optimized top piece has a relatively small thermal mass, such thattemperature corrections by the cooling system may be substantiallysynchronized.

An appropriate set of gases is flowed into chamber 202 from gasdistribution system 222. These plasma processing gases may besubsequently ionized to form a plasma 210, in order to process (e.g.,etch or deposition) exposed areas of substrate 224, such as asemiconductor substrate or a glass pane, positioned with edge ring 215on an electrostatic chuck (chuck) 226. Gas distribution system 222 iscommonly comprised of compressed gas cylinders (not shown) containingplasma processing gases (e.g., C₄F₈, C₄F₆, CHF₃, CH₂F₃, CF₄, HBr, CH₃F,C₂F₄, N₂, O₂, Ar, Xe, He, H₂, NH₃, SF₆, BCl₃, Cl₂, WF₆, etc.).

Induction coil 231 is separated from the plasma by a dielectric window204, and generally induces a time-varying electric current in the plasmaprocessing gases to create plasma 220. The window both protectsinduction coil from plasma 220, and allows the generated RF field 242 topenetrate into the plasma processing chamber. Further coupled toinduction coil 231 is matching network 232 that may be further coupledto RF generator 234. Matching network 232 attempts to match theimpedance of RF generator 234, which typically operates at about 13.56MHz and about 50 ohms, to that of the plasma 220. Additionally, a secondRF energy source 238 may also be coupled through matching network 236 tothe substrate 224 in order to create a bias with the plasma, and directthe plasma away from structures within the plasma processing system andtoward the substrate.

Generally, some type of cooling system 240 is coupled to chuck 216 inorder to achieve thermal equilibrium once the plasma is ignited. Thecooling system itself is usually comprised of a chiller that pumps acoolant through cavities within the chuck, and helium gas pumped betweenthe chuck and the substrate. In addition to removing the generated heat,the helium gas also allows the cooling system to rapidly control heatdissipation. That is, increasing helium pressure subsequently alsoincreases the heat transfer rate. Most plasma processing systems arealso controlled by sophisticated computers comprising operating softwareprograms. In a typical operating environment, manufacturing processparameters (e.g., voltage, gas flow mix, gas flow rate, pressure, etc.)are generally configured for a particular plasma processing system and aspecific recipe.

In addition, a heating and cooling plate 246, or other process relatedhardware, may operate to control the temperature of the top piece 244,or process conditions, of the plasma processing apparatus 202 such thatthe inner surface of the optimized top piece 244, which is exposed tothe plasma during operation, is maintained at a controlled temperature.However, unlike a non-optimized top piece, heating and cooling plate246, or other process related hardware, is positioned such that it isshielded from electromagnetic field 242 by the optimized top piece.

As previously described, as a high frequency power is applied from theRF power generator 234 to the coil 231, an electromagnetic field 242 isgenerated, which subsequently generates an inductive current 211 thatcreates and maintains the plasma. Since optimized top piece 244 shieldselectromagnetic field 242 from heating and cooling plate 246, or otherprocess related hardware, the resulting electromagnetic field 211 andhence the uniformity of plasma 220 may be better optimized. That is, theresulting electric field may become less distorted which may result in amore optimum uniform plasma density across the substrate, potentiallyimproving yield (e.g., reducing faceting, etc.).

Referring now to FIG. 3A, a simplified diagram of an optimized top piece244 is shown, according to one embodiment of the present invention.Portion 302 represents approximately 80% of the mass of thenon-optimized top piece, and is non-process critical. Since only theouter surface has been modified, the internal shape 304 substantiallymatches electrical, gas flow, and plasma containment characteristics ofa non-optimized top piece.

Referring now to FIG. 3B, a simplified diagram of an optimized top piece244 is shown, according to one embodiment of the present invention.Mounting locations 312 allow the coupling of alignment brackets that maybe removed during cleaning, in order to minimize part cost and cleaningsolution contamination. The set of handles 313 are integrated directlyinto the top piece, and provide a specific point from which to pick upand handle the top piece to order to minimize operator contact with theprocess sensitive areas of the chamber. In addition, the set ofalignment holes 314 allows for the alignment and mounting of the RF coildirectly to the chamber.

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations, and equivalents whichfall within the scope of this invention. For example, although thepresent invention has been described in connection with plasmaprocessing systems from Lam Research Corp. (e.g., Exelan™, Exelan™ HP,Exelan™ HPT, 2300™, Versys™ Star, etc.), other plasma processing systemsmay be used. This invention may also be used with substrates of variousdiameters (e.g., 200 mm, 300 mm, etc.). Also, materials other thanaluminum may be used, such as ceramics.

Advantages of the invention include an apparatus for an optimized plasmachamber top piece. Additional advantages may include optimization ofworker ergonomic safety and plasma process operational characteristics.

Having disclosed exemplary embodiments and the best mode, modificationsand variations may be made to the disclosed embodiments while remainingwithin the subject and spirit of the invention as defined by thefollowing claims.

1. A plasma processing system for processing a substrate, comprising: abottom piece including a chuck configured for holding said substrate; aninduction coil configured to generate an electromagnetic field in orderto create a plasma for processing said substrate; and an optimized toppiece coupled to said bottom piece, said top piece further configuredfor a heating and cooling system; wherein said heating and coolingsystem is substantially shielded from said electromagnetic field by saidoptimized top piece, and said optimized top piece can substantially behandled by a single person.
 2. The plasma processing system of claim 1,wherein said optimized top piece substantially complies with a set ofSEMI ergonomic safety standards for a part handled by said singleperson.
 3. The plasma processing system of claim 1, wherein the weightof said optimized top piece is about 80% less than the weight of anon-optimized top piece.
 4. The plasma processing system of claim 1,wherein said single person can easily manipulate the optimized top piecewithout the use of a lifting apparatus.
 5. The plasma processing systemof claim 1, wherein said optimized top piece is comprised of aluminum.6. The plasma processing system of claim 1, wherein said optimized toppiece is comprised of ceramic.
 7. The plasma processing system of claim1, wherein said optimized top piece does not include plastic.
 8. Theplasma processing system of claim 1, wherein said optimized top pieceincludes an inner surface area exposed to said plasma, where said innersurface area of said optimized top piece is substantially the same as anon-optimized top piece.
 9. The plasma processing system of claim 1,wherein said optimized top piece comprises a set of integrated handles.10. The plasma processing system of claim 1, wherein said optimized toppiece comprises a set of alignment holes.
 11. The plasma processingsystem of claim 1, wherein said substrate comprises a wafer.
 12. Theplasma processing system of claim 1, wherein said substrate comprises aglass panel.
 13. A plasma processing system for processing a substrate,comprising: a bottom piece including a chuck configured for holding saidsubstrate; an induction coil configured to generate an electromagneticfield in order to create a plasma for processing said substrate; and aoptimized top piece coupled to said bottom piece, said top piece furtherconfigured for a heating and cooling system; wherein said heating andcooling system is substantially shielded from said electromagnetic fieldby said optimized top piece, and said optimized top piece substantiallycomplies with a set of SEMI ergonomic safety standards for a parthandled by a single person.